Electric current transfer structure including contact balls



R. E. FRINK Jan. 31, 1967 ELECTRIC CURRENT TRANSFER STRUCTURE INCLUDINGCONTACT BALLS 2 Sheets-Sheet 1 Filed Oct. 13, 1965 k mm T W Q WE. W m svSB u Du ATTORNEY WITNESSES Jan. 31, 1967 R. E. FRINK ELECTRIC CURRENTTRANSFER STRUCTURE INCLUDING CONTACT BALLS Filed Oct. 15, 1965 O P E RATN G MECHANISM 2 Sheets-Sheet 2 F IG. 4

United States Patent Ofifrce 3,301,986 Patented Jan. 31, 1967 ELECTRICCURRENT TRANSFER STRUCTURE INCLUDING CONTACT BALLS Russell E. Frinlr,Forest Hills, Pittsburgh, Pa., assignor to Westinghouse ElectricCorporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Oct.13, 1965, Ser. No. 495,475

17 Claims. (Cl. 200166) This invention relates to electrical apparatusand, more particularly, to means for transferring electrical currentbetween relatively movable current carrying parts.

In certain types of electrical apparatus, such as circuit interrupters,it is necessary to transfer relatively large magnitudes of electricalcurrent between relatively movable current carrying parts of theapparatus. For example, during a circuit interrupting operation ofcertain types of circuit interrupters or circuit breakers, it may benecessary to efficiently transfer thousands of amperes betweenrelatively movable current carrying parts of the circuit interrupter. Ithas been found that structures provided in the past for this purpose aresubject to certain limitations when called upon to perform repetitiveoperations. For example, an electrical contact which is designed tocarry high momentary current is limited as to the maximum current thatcan be carried through each point of contact between relatively movableparts because of blowoff forces created by current converging to thepoint of contact. Considering each point of contact which carriescontinuous current between relatively movable, current carrying parts,the voltage drop at each point of contact is usually larger than thevoltage drop through the balance of the parts.

Certain problems may also arise due to the mechanical failure of thestructure such as a flexible conductor or the relatively large size ofthe structure required to transfer a relatively large magnitude ofcurrent. It is therefore desirable to provide an improved means fortransferring relatively large magnitudes of current between relativelymovable conducting parts in an electrical apparatus which is morecompact in size and which overcomes certain other problems of structuresof the same general type which have been employed in the past.

It is an object of this invention to provide a new and improved meansfor carrying electrical current between two relatively movable currentcarrying parts.

Another object of this invention is to provide a more compact structurefor transferring relatively large electrical currents between relativelymovable current carrying parts.

A further object of this invention is to provide a circuit interrupterincluding improved means for carrying electrical current betweenrelatively movable, current carrying parts of the interrupter.

Other objects of the invention will, in part, be obvious and will, inpart, appear hereinafter.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconjunction with the accompanying drawings, in which:

FIGURE 1 is a front elevational view, partly in section, of a currentjoint or structure embodying the principal features of the invention;

FIG. 2 is a view in section of the current carrying apparatus shown inFIG. 1, taken along the line II-II with a portion of the apparatusbroken away;

FIG. 3 is a diagrammatic view of a circuit interrupter including thecurrent carrying apparatus shown in FIGS. 1 and 2; and

FIG. 4 is a diagrammatic view of another type of circuit interrupterincluding the current carrying apparatus shown in FIGS. land 2.

Referring now to the drawings and FIGS. 1 and 2 in particular, there isillustrated a current transfer means 10 which is adapted to transferrelatively large magnitudes of electrical current between relativelymovable, current carrying parts or members. In general, the currenttransfer structure 10 comprises a first electrical conductor which, inthis instance, includes the tubular conductor 30 and the associatedconducting end ring 62 and a second electrical conductor which, in thisinstance, is an electrically conducting shaft or rod C1 which isdisposed within or to pass through the first electrical conductor.

In order to provide a housing for a plurality of electrically conductingballs 42 and 44, as will be explained hereinafter, at least a portion ofthe inner surface of the tubular conductor 30 as indicated at 30E isshaped or formed to provide an annular space or chamber between thetubular conductor 30 and the conducting shaft C1, as indicated at 65 inFIG. 1 In order to retain the conducting balls 42 and 44 in the annularspace 65 between the tubular conductor 30 and the conducting shaft C1 aswell as for other purposes, the conducting ring 62 is disposed at theleft end of the tubular conductor 30, as viewed in FIG. 1, tosubstantially close off the left end of the annular space or chamber 65with the conducting shaft C1 also disposed within or passing through theconducting ring 62. It is to be noted that the balance of the innersurface of the tubular conductor 30 as indicated at 30G is slightlylarger in size than the outer surface of the conducting shaft C1 and isof the same configuration as the cross-section of the conducting shaftC1 which, in this instance, is substantially circular. In order toretain the conducting ring 62 in assembled relationship with the tubularconductor 30, the internally threaded end cap 52 is disposed around andengages the externally threaded portion 30B provided at the left-end ofthe tubular conductor 30, as best shown in FIG. l.

In order to provide a pair of contact areas or surfaces on the innersurfaces of the conducting ring 62 and the tubular conductor 30 whichare spaced along the longitudinal dimension of the conducting shaft C1,the inner surfaces of the conducting ring 62 and the tubular conductor30 are oppositely beveled or chamfered at the opposite ends of thegenerally annular space 65 as indicated at 62A and 30F, respectively,preferably at an angle of substantially 45 with respect to thelongitudinal axis of the conducting shaft C1.

Considering the tubular conductor 30 and the conducting ring 62, takentogether as a first overall outer couductor, and the conducting shaft orrod C1 as a second conductor, it is important to note that at least oneof the overall conductors is relatively movable with respect to theother overall conductor. More specifically, the conducting shaft or rodC1 may be rectilinearly or rotatably movable with respect to the firstoverall conductor which includes the tubular conductor 30 and theconducting ring 62; the first overall conductor may be rectilinearly orrotatably movable with respect to the conducting shaft C1, or bothoverall conductors may be rectilinearly or rotatably movable withrespect to the other conductor. In order to provide a plurality ofcurrent carrying paths between the conducting shaft C1 and the firstoverall conductor just described during the movement of the shaft Clwith respect to the first overall conductor or during the movement ofthe first overall conductor with respect to the shaft C1, a plurality ofpairs of electrically conducting balls 42 and 44 are disposed in theannular space or chamber 65 between the tubular conductor 30 and theconducting ring 62 and the conducting shaft C1 around the periphery ofthe conducting shaft C1, as shown in FIG. 2. The balls 42 and 44 whichmake up each pair of conducting balls are spaced from one another alongthe longitudinal dimension of the conducting shaft C1 adjacent to therespective contact areas 62A and 30F on the conducting ring 62 and thetubular conductor 30, respectively.

In order to resiliently bias each pair of conducting balls 42 and 44into contact making engagement with the contact areas 62A and 30F,respectively, and also with spaced points on the periphery of theconducting shaft C1, a plurality of separate biasing means 66 aredisposed in the annular space 65 between the respective pairs ofconducting balls 42 and 44. Each biasing means 60 comprises a pair ofspaced spring seat members 64 and 66, each of the spring seat members 64and 66 including a curved or part-spherical surface which bears againstone of the associated conducting balls 42 or 44, respectively. Acompression spring 68 is disposed between each pair of spring seatmembers 64 and 66 with the ends of the spring 68 bearing against theshoulders provided on the respective spring seat members 64 and 66 witha portion of each of the spring seat members 64 and 66 projecting insidethe biasing spring 68, as illustrated. The spring 68 applies oppositelydirected biasing forces to the associated conducting balls 42 and 44 todrive or push the balls 42 and 44 into good contact making engagementwith the contact areas 62A and 30F respectively and into good contactmaking engagement with spaced points on the conducting shaft C1. Since alarge number of current carrying paths may be provided in a relativelycompact structure as disclosed, the contact pressure required on each ofthe conducting balls 42 and 44 may be kept relatively low to therebyreduce the mechanical wear on the parts that might otherwise result.

In order to maintain the plurality of pairs of conducting balls 42 and44 in spaced relation around the periphery of the conducting shaft C1,the portion of the tubular conductor 30 as indicated at 30E between thecontact areas 62A and 30F may include a plurality of axially extendinggrooves or flutes, as indicated at 30H in FIG. 2, with each pair ofconducting balls 42 and 44 and the associated biasing means 60 being atleast partially disposed in the associated groove on the inner surfaceof the portion 30E of the tubular conductor '30.

In order to retain an additional conducting member 22 in assembledrelationship 'with the tubular conductor 30, the other end of thetubular conductor 30 as indicated at 30C may be externally threaded toreceive a retaining nut 24 within the conducting member 22 beingdisposed between a shoulder 30A provided on the external surface of thetubular conductor 36 and the retaining nut 24 which may be tightenedagainst the conducting member 22. The conducting member 22 will then beretained in assembled relationship with the outer tubular conductor 30for movement therewith.

In the operation of the current transfer structure 10, each of theconducting balls 42 and 44 forms a first point contact on the one handwith one of the respective contact areas 62A or 30F on the conductingring 62 or on the tubular conductor 30, respectively, and on the otherhand forms a point contact with the conducting shaft or rod C1. Thesepoint contacts result from the biasing action of the biasing means 60which drives the conducting balls 42 and 44 at the opposite ends of eachbiasing means 60 into the wedge-shaped or tapered spaces which result atthe ends of the annular space 65. In other words, a first set of currentcarrying paths is formed which extends from the tubular conductor 34),into the conducting ring 62, and then to the conducting shaft C1 througha plurality of paths spaced around the periphery of the shaft C1 throughthe conducting balls 42. At the opposite end of the annular space 65, asimilar set of current carrying paths result which extends from thetubular conductor 30, through the spaced conducting balls 44 around theperiphery of the shaft C1 and then into the conducting shaft C1. It hasbeen found that during the operation of a current transfer structurewhich was constructed, when the conducting shaft C1 moves relative tothe tubular conductor 30 and the conducting ring 62, either in areciprocating manner or in a rotating fashion, the conducting balls 42and 44 remain substantially stationary with respect to the conductingshaft C1 since the frictional forces exerted on the balls 42 and 44 bythe conducting ring 62 and the tubular conductor 30, respectively, andby the spring seat members 64 and 66, respectively, which tend tomaintain the conducting balls 42 and 44 in a relatively stationaryposition with respect to the shaft C1 are greater than the frictionalforces exerted on the balls 42 and 44 which might otherwise tend tocause the balls 44 and 42 to rotate in place.

Referring now to FIG. 3, there is illustrated a circuit interrupter orcircuit breaker CB which includes the current transfer structure 10 andwhich is adapted when closed to form a closed circuit between the lineconductors L1 and L2, indicated diagrammatically. As illustrated, thecircuit interrupter CB includes a relatively stationary contact means120 which comprises a plurality of relatively stationary contact members122 which are electrically connected to the line conductor L1. Therelatively stationary contact means 120 is adapted to be engaged by amovable conducting member C1 which forms part of a current transferstructure 10, as previously described in detail. The free end .of themovable conducting member C1 may be curved as indicated at 128 tofacilitate the entrance of the movable conducting member C1 into thestationary contact fingers 122 which may be resiliently mounted. Themovable conducting member C1 is electrically connected to the other lineconductor L2 through the conductor member 22, the tubular conductor 30and the conducting ring 62 which forms part of the current transferstructure 10 and the conducting balls 42 and 44 which form part of thecurrent transfer structure 10, as previously described.

In order to actuate the movable conducting member C1 into and out ofengagement with respect to the stationary contact means 120 to therebyopen and close the electric circuit between the line conductors L1 andL2, the operating mechanism as indicated at is operatively connected tothe movable conducting members C1 through an operative connection, asindicated diagrammatically at 112, and through an electricallyinsulating member, as indicated at 114 in FIG. 3. It is to be noted thatin this circuit interrupter CB, the conducting shaft C1 is arranged forreciprocating or rectilinear movement with respect to the tubularconductor 30 and the conducting ring 62 which forms part of the currenttransfer structure 10 with the tubular conductor 30 and the conductingring 62 being held in a relatively stationary position with respect tothe conducting shaft C1.

Referring now to FIG. 4, there is allustrated a second circuitinterrupter or disconnecting switch SW which includes the currenttransfer structure 10 and which is adapted when closed to complete anelectric circuit which extends between the line conductors L1 and L2,indicated diagrammatically in FIG. 4. The disconnecting switch SW asillustrated includes a plurality of stationary contact members 222 whichare electrically connected to the line conductor L2. The disconnectingswitch SW also includes a movable conducting member or switch blade 22which is mounted on the tubular conductor 30 which forms part of thecurrent transfer structure 10, as previously described, for movementwith the tubular conductor 30 when the switch blade 22 is actuated by asuitable operating mechanism (not shown). The other line conductor L1 iselectrically connected to the switch blade 22 through a conducting shaftor rod C2 which is disposed within or to pass through the tubularconductor 30, through the plurality of conducting balls 42 and 44 whioliare included as part of the current transfer structure 10 and throughthe conducting ring 62 and the tubular conductor 30 which make up partof the current transfer structure 10 to the switch blade 22. Asillustrated in FIG. 4, the opposite ends of the conducting shaft C2 maybe journaled in suitable bearing supports 212 and 214 which are disposedaround the conducting shaft C2 at the opposite ends of the shaft C2, asshown in FIG. 4.

In the operation of the disconnecting switch SW, the switch blade 22which moves with the tubular conductor 30 .of the current transferstructure may be rotated into or out of engagement with the stationarycontact members 222 to thereby open and close the electric circuitbetween the line conductors L1 and L2.

It is to be understood that in a current transfer structure asdisclosed, a single set of conducting balls may be provided around theperiphery of the conducting shaft C1 with the biasing means 60 bearingagainst a substantially flat surface on the conducting ring 62 ratherthan including an additional set of conducting balls which bear againsta beveled inner surface on the conducting ring 62 as in the preferredembodiment. It is also to be understood that a separate means may beprovided in the annular space 65 for maintaining the pairs of balls inspaced relation around the periphery of the conducting shaft C1. Inother words, a ring shaped member having a plurality of axiallyextending grooves on its inner surface may be disposed between the balls42 and 44 and the inner surface of the tubular conductor 30 and may beformed from an electrically insulating material where desired since theconducting balls 42 and 44 in a current transfer structure as disclosedcarry current between the conducting shaft C1 and the conducting ring 62and the tubular couductor 30 only through the beveled contact areas atthe ends of the annular space 65. It is also to be understood that theconducting ring 62 may be formed integrally with the tubular conductor30 to form an overall outer conductor since the purpose of providing aseparate conducting ring 62 is to facilitate assembly of the conductingballs 42 and 44 in the annular space 65 along with the separate biasingmeans 60 which are provided with each pair of conducting balls 42 and44. It is to be further understood that the balls 42 and 44 may behollow in a particular application or that a central core of electricalinsulating material may be provided with a suitable layer ofelectrically conducting material on the outer surface of each of suchballs.

Considering the circuit interrupters disclosed, it is to be understoodthat a separate contact means may be mounted on the movable conductingmember provided or the contact means may be formed integrally with themovable conducting memben. I V

This apparatus embodying the teachings of this invention has severaladvantages. For example, a current transfer structure is disclosed whichis extremely compact compared with current transfer structures of thesame general type which have been employed in the past. It has beenfound that extremely large magnitudes of electric current may betransferred between relatively movable parts in an electrical apparatusin an extremely small space. Another advantage of the disclosedcurrenttransfer structure is that the resilient biasing means provided for thecontact balls 42 and 44 compensates for or permits a limitedmisalignment between the relatively movable parts which are required ina particular application since a limited degree of misalignment betweenthe relatively movable current carrying parts in electrical apparatus iscompensated for by movement of the conducting balls into or out of thetapered or wedge shaped recesses provided at the opposite ends of theannular space in the disclosed current transfer structure. Since arelatively large number of current paths may be provided in vention maybe made without departing from the spirit and scope thereof, it isintended that all of the matter contained in the foregoing descriptionor shown in the accompanying drawing shall be interpreted asillustrative and not in a limiting sense.

I claim as my invention:

1. In combination, a tubular electrical conductor having an innersurface, another electrical conductor disposed within the tubularconductor, at least one of the conductors being movable with respect tothe other conductor, a portion of the inner surface of the tubularconductor shaped to provide a generally annular space between theconductors, at least one end of the portion beveled to provide a contactarea on the inner surface of the tubular conductor, a plurality ofelectrically conducting balls disposed in the annular space around theperiphery of said another conductor adjacent to the contact area on theinner surface of the tubular conductor, and separate means disposed inthe annular space for biasing each ball into contact malking engagementwith the contact area on the inner surface of the tubular contact andwtih said another conductor.

2. A combination as claimed in claim 1 wherein means is provided in theannular space for maintaining the plurality of balls in spaced relationaround the periphery of said another conductor.

3. A combination as claimed in claim 1 wherein the inner surface of thetubular conductor is provided with a plurality of axially extendinggrooves in which the re spective balls are at least partially disposedfor maintaining the balls in spaced relation around the periphery ofsaid another conductor.

4. In combination, a tubular electrical conductor having an innersurface, another electrical conductor disposed within the tubularconductor, at least. one of the conductors being movable relative to theother conductor, a portion of the inner surface of the tubular conductorshaped to provide an annular space between the conductors, the ends ofsaid portion oppositely beveled to provide a pair of spaced contactareas on the inner surface of the tubular conductor, a plurality ofpairs of spaced, electrically conducting balls disposed in the annularspace around the periphery of said another conductor adjacent to therespective contact areas, and separate means disposed in the annularspace between each pair of conducting balls for biasing each pair ofconducting balls into contact making engagement with the respectivecontact areas on the inner surface of the tubular conductor and withsaid another conductor.

5. A combination as claimed in claim 4, wherein the portion of the innersurface of the tubular conductor includes a plurality of axiallyextending grooves intermediate the beveled ends with each pair of ballsbeing at least partially disposed in one of the grooves.

6. A combination as claimed in claim 4, wherein a separate means isprovided between the plurality of pairs of balls and the inner surfaceof the tubular conductor for maintaining the pairs of balls in spacedrelation around the periphery of said another conductor.

7. A current conducting assembly comprising a generally cylindrical,electrically conducting member having a central opening extendingtherethr-ough, an electrically conducting shaft disposed to passthroughthe central opening and being relatively movable with respect to theconducting member, at least part of said central opening enlarged todefine an annular space between the conducting member and the conductingshaft, the portions of the conducting member adjacent the opposite endsof the annular space oppositely beveled at an angle of substantially 45with respect to the longitudinal dimension of the shaft to define twospaced contact areas on the conducting member, a plurality of pairs ofspaced conducting balls disposed around the periphery of the shaft inthe annular space and separate means for biasing each pair of ballsapart into contact making engagement with 7 both the shaft and therespective contact areas of the conducting member.

8. A combination as claimed in claim 7 wherein means is providedintermediate the plurality of pairs of balls I and the conducting memberfor retaining the pairs of balls in spaced relation around the peripheryof the shaft.

9. A circuit interrupter comprising a tubular electrical conductorhaving an inner surface, another electrical conductor disposed withinthe tubular conductor, at least one of the conductors being movable withrespect to the other conductor, contact means mounted on the movableconductor for movement therewith, a relatively stationary contactdisposed in the path of movement of the movable contact means forengagement therewith and for disengagement therefrom, a portion of theinner surface of the tubular conductor formed to provide an annularspace between the conductors, the ends of the portion oppositelychamfered to provide two space contact areas on the inner surface of thetubular conductor, a plurality of pairs of electrically conducting ballsspaced along said another conductor and disposed in the annular spacearound said another conductor adjacent to the respective contact areas,and separate means disposed in the annular space for biasing each pairof balls away from each other into engagement with the respectivecontact areas and said another conductor.

10. A combination as claimed in claim 9 wherein the ends of the portionof the tubular conductor are oppositely chamfered at an angle ofsubstantially 45 with respect to the longitudinal dimension of saidanother conductor.

11. A combination as claimed in claim 9, wherein a separate, generallyannular member is provided between the inner surface of the tubularconductor and said another conductor for maintaining the respectivepairs of balls and the associated biasing means in spaced relationaround the periphery of said another conductor.

12. A circuit interrupter comprising a tubular electrical conductorhaving an inner surface, an electrically conducting shaft disposedwithin the tubular conductor and being reciprocally movable with respectto the tubular conductor, contact means mounted on the shaft formovement with the shaft, a relatively stationary contact disposed in thepath of movement of the movable contact means, a portion of the innersurface of the tubular conductor formed to provide a generally annularspace between the tubular conductor and the shaft, at least one end ofthe portion beveled to provide a contact area on the inner surface ofthe tubular conductor, a plurality of electrically conducting ballsdisposed in the annular space around the periphery of the shaft adjacentto the contact area on the inner surface of the tubular conductor, andseparate means for biasing each ball into contact making engagement withthe contact area on the inner surface of the tubular conductor and withsaid another conductor.

13. A combination as claimed in claim 12 wherein the inner surface ofthe tubular conductor includes a plurality of axially extending groovesin which the respective balls are at least partially disposed formaintaining the balls in spaced relation around the shaft.

14. A circuit interrupter comprising a tubular electrical conductorhaving an inner surface, an electrically con- 8 ducting shaft disposedwithin the tubular conductor and being reciprocally movable with respectto the tubular conductor, contact means mounted on the shaft formovement with the shaft, a relatively stationary contact disposed in thepath of movement of the movable contact means, a portion of the innersurface of the tubular conductor formed to provide a generally annularspace between the tubular conductor and the shaft, the ends of theportion oppositely beveled to provide two spaced contact areas on theinner surface of the tubular conductor, a plurality of pairs ofelectrically conducting balls spaced along the shaft in the annularspace adjacent to the respective contact areas, and separate meansdisposed in the annular space for biasing each pair of balls away fromeach other into engagement with the respective contact areas and withthe shaft.

15. A combination as claimed in claim 13 wherein the inner surface ofthe tubular conductor includes a plurality of axially extending groovesin which the respective pairs of balls are at least partially disposedfor maintaining the pairs of balls in spaced relation around theperiphery of the shaft.

16. A circuit interrupter comprising a tubular electrical conductorhaving an inner surface, an electrically conducting shaft disposedwithin the tubular conductor, the tubular conductor being rotatableabout the shaft, an electrically conducting blade mounted on the tubularconductor for rotation therewith, a relatively stationary contactdisposed in the path of movement of the blade for engagement therewith,a portion of the inner surface of the tubular conductor shaped toprovide agenerally annular space between the tubular conductor and theshaft, the ends of the portion oppositely chamfered to provide twospaced contact areas on the inner surface of the tubular conductor, aplurality of pairs of electrically conducting balls disposed in theannular space and spaced along the shaft adjacent to the respectivecontact areas, and separate means disposed in the annular space forbiasing each pair of balls away from each other into engagement with therespective contact areas and with the shaft.

17. A combination as claimed in claim 16 wherein the inner surface ofthe tubular conductor includes a plurality of axially extending groovesin which the respective pairs of balls are at least partially disposedfor maintaining the pairs of balls in spaced relation around theperiphery of the shaft.

References Cited by the Examiner FOREIGN PATENTS 1,197,958 8/1965Germany.

References Cited by the Applicant UNITED STATES PATENTS 2,359,055 9/1944 Schwager et al. 3,127,492 3/1964 Date.

FOREIGN PATENTS 1,913,394 4/1965 Germany.

0 ROBERT K. SCHAEFER, Primary Examiner.

H. O. JONES, Assistqnt Examiner,

1. IN COMBINATION, A TUBULAR ELECTRICAL CONDUCTOR HAVING AN INNERSURFACE, ANOTHER ELECTRICAL CONDUCTOR DISPOSED WITHIN THE TUBULARCONDUCTOR, AT LEAST ONE OF THE CONDUCTORS BEING MOVABLE WITH RESPECT TOTHE OTHER CONDUCTOR, A PORTION OF THE INNER SURFACE OF THE TUBULARCONDUCTOR SHAPED TO PROVIDE A GENERALLY ANNULAR SPACE BETWEEN THECONDUCTORS, AT LEAST ONE END OF THE PORTION BEVELED TO PROVIDE A CONTACTAREA ON THE INNER SURFACE OF THE TUBULAR CONDUCTOR, A PLURALITY OFELECTRICALLY CONDUCTING BALLS DISPOSED IN THE ANNULAR SPACE AROUND THEPERIPHERY OF SAID ANOTHER CONDUCTOR ADJACENT TO THE CONTACT AREA ON THEINNER SURFACE OF THE TUBULAR CONDUCTOR, AND SEPARATE MEANS DISPOSED INTHE ANNULAR SPACE FOR